Method of determining an orthodontic treatment

ABSTRACT

A method of determining an optimal switchover moment for a hybrid orthodontic treatment of teeth. Creation of a digital three-dimensional model of at least part of a dental arch. Deformation of the initial reference model until the tooth models are in a target position. Acquisition of at least one two-dimensional image of the teeth. Deformation of the initial reference model until the at least one updated image corresponds to the initial reference model. Determination, from the updated reference model and from said target reference model, of a plurality of remaining-treatments for moving the teeth from their position represented in the updated reference model into their position represented in the target reference model. Determination of a profile including at least one value for an evaluation parameter. Evaluation of each profile by an evaluation rule. Determination the profile of which is optimal for replacing an orthodontic appliance with an aligner.

TECHNICAL FIELD

The present invention relates to a method of determining a switchovermoment beyond which a patient wearing an arch wire and bracketsorthodontic appliance will switch over to wearing one or moreorthodontic aligners.

The invention also relates to a computer program for implementing thismethod.

PRIOR ART

Among orthodontic appliances, a distinction is made between, on the onehand, arch wire and brackets orthodontic appliances and, on the otherhand, orthodontic aligners.

An orthodontic appliance with arch wire and brackets comprises fixings,referred to as “brackets”, fixed to the teeth and connected to oneanother by means of an arch wire, conventionally made from ashape-memory material. It acts quickly to move the teeth of the patientbeing treated. However, this action slows progressively over time andthe patient needs to visit the orthodontist regularly in order to modifythe adjustment of the arch wire, or change same. Furthermore, anorthodontic appliance of the arch wire and brackets type is oftenvisually unattractive.

A tray-like device, more properly known as an “aligner”, conventionallycomes in the form of a removable monobloc appliance, conventionally madeof a transparent polymer. It comprises a tray shaped in such a way thatseveral teeth of a dental arch, generally all the teeth of a dentalarch, can be housed therein. The shape of the tray is tailored to holdthe aligner in position on the teeth while at the same time applying anaction towards correcting the positioning of certain teeth. Anorthodontic aligner has an initial action that is far slower than thatof an arch wire and brackets orthodontic appliance. However, the alignermay advantageously be replaced by the patient himself. Furthermore,aligners are more discreet than arch wire and brackets appliances.

A “hybrid” orthodontic treatment makes it possible to enjoy theadvantages of each of these two types of orthodontic appliance. Usually,it comprises a first treatment phase during which the patient wears anorthodontic appliance or “arch wire phase”, followed, from a switchovermoment onwards, by a second phase of treatment using orthodonticaligners, or “aligners phase”. The treatment then continues usingaligners.

There is constantly a need for a method that makes it possible tooptimize a hybrid treatment, particularly in order to reduce theduration thereof.

One object of the invention is to provide a response to this need.

SUMMARY OF THE INVENTION

The invention provides a method of determining an optimal switchovermoment for a hybrid orthodontic treatment of teeth of a patient, saidmethod comprising the following operations:

-   -   1) for preference at the start of the treatment or before the        start of the treatment, creation of a digital three-dimensional        model of at least part of a dental arch bearing said teeth, or        “initial reference model” and, for each of said teeth,        definition of a digital three-dimensional reference model of        said tooth in the initial reference model, or “tooth model”;    -   2) after operation 1), preferably at the start of the treatment        or before the start of the treatment, deformation of the initial        reference model, by moving the tooth models, until said tooth        models are in a target position, so as to obtain a “target        reference model”,    -   3) after operation 2), at some moment in a phase of the        treatment during which the patient wears an arch wire and        brackets orthodontic appliance, referred to as “current moment”,        acquisition of at least one two-dimensional image of said teeth,        referred to as “updated image”, under the actual acquisition        conditions;    -   4) deformation of the initial reference model, by moving the        tooth models, until said at least one updated image corresponds        to a view of the initial reference model thus deformed, referred        to as “updated reference model”, the search for the updated        reference model preferably being performed by means of a        meta-heuristic, preferably evolutionary method, preferably by        simulated annealing;    -   5) determination, from said updated reference model and from        said target reference model, of a plurality of        remaining-treatment scenarios for moving said teeth from their        position represented in the updated reference model into their        position represented in the target reference model, each        scenario comprising, from a switchover moment onwards, at least        one phase of treatment using an orthodontic aligner;    -   6) determination, for each scenario, of a profile comprising at        least one value for an evaluation parameter selected from the        group formed of:        -   the duration of the remaining treatment of said scenario;        -   the duration of the entire treatment;        -   a clinical-complexity factor, or “severity score”;        -   a pain factor for the remaining treatment of said scenario,        -   a pain factor for the entire treatment;        -   the duration of the phase or phases of treatment using an            arch wire and brackets orthodontic arch wire during the            remaining treatment;        -   a comfort factor for the remaining treatment of said            scenario,        -   a comfort factor for the entire treatment;        -   a cost of the remaining treatment of said scenario,        -   a cost of the entire treatment,        -   a function of the preceding evaluation parameters;    -   7) evaluation of each profile by means of an evaluation rule;        and    -   8) determination, from the scenario the profile of which is        optimal, or “optimal scenario” of an optimal switchover moment        for replacing the arch wire and brackets orthodontic appliance        with an aligner.

As will be seen in greater detail in what follows of the description, amethod according to the invention allows the treatment to be adapted tosuit specific conditions, and in particular, conditions imposed by thepatient. For example, if the patient imposes a maximum treatmentduration of six months and an aligner phase that is as long as possible,the method according to the invention makes it possible to test variousscenarios in order to search for the profile that best meets this need.

Operations 5) to 8) may or may not be successive. When they aresuccessive, they are referred to as “steps” 5′) to 8′) respectively.

In a preferred embodiment, they are imbricated and constitute thefollowing successive steps 5″) to 8″):

-   -   5″) determination, from said updated reference model and from        said target reference model, of a remaining-treatment scenario        for moving said teeth from their position represented in the        updated reference model into their position represented in the        target reference model, a remaining-treatment scenario        comprising, from a switchover moment onwards, at least one phase        of treatment using an orthodontic aligner;    -   6″) determination, for said scenario, of a profile comprising at        least one value for an evaluation parameter selected from the        group formed of:        -   the duration of the remaining treatment of said scenario;        -   the duration of the entire treatment;        -   a clinical-complexity factor, or “severity score”;        -   a pain factor for the remaining treatment of said scenario;        -   a clinical-complexity factor;        -   a pain factor for the entire treatment;        -   the duration of the phase or phases of treatment using an            arch wire and brackets orthodontic arch wire during the            remaining treatment;        -   a comfort factor for the remaining treatment of said            scenario,        -   a comfort factor for the entire treatment;        -   a cost of the remaining treatment of said scenario,        -   a cost of the entire treatment,        -   a function of the preceding evaluation parameters;    -   7″) evaluation of the profile by means of an evaluation rule        and, if the profile is not optimal with reference to the        evaluation rule, determination of a new remaining-treatment        scenario and resumption from step 6″);    -   8″) determination, from the scenario the profile of which is        optimal, or “optimal scenario” of an optimal switchover moment        for replacing the arch wire and brackets orthodontic appliance        with an aligner.

For preference, a method according to the invention also has one or moreof the following optional features:

-   -   over 5, 10, 50 or 100 scenarios are determined in operation 5);    -   in operation 3), the updated image is taken by means of an image        acquisition apparatus selected from the group consisting of a        mobile telephone, a connected camera, a smartwatch, a tablet        and/or a desktop or laptop personal computer;    -   operation 4) comprises the following steps:        -   c) analysis of the updated image and creation of an updated            map relating to discriminating information;        -   d) optionally, determination, for the updated image, of            rough virtual acquisition conditions approximating the            actual acquisition conditions of said updated image;        -   e) search, in the case of the updated image, for an updated            reference model corresponding to the positioning of the            teeth at the time of the acquisition of the updated image,            the search preferably being carried out by means of a            meta-heuristic, preferably evolutionary method, preferably            by simulated annealing;    -   step e) comprises the following steps:        -   e1) definition of a reference model to be tested as being            the initial reference model, then        -   e2) following the subsequent steps, testing virtual            acquisition conditions with the reference model to be tested            in order to achieve a fine approximation of said actual            acquisition conditions;            -   e21) determining virtual acquisition conditions to be                tested;            -   e22) creation of a two-dimensional reference image of                the reference model to be tested under said virtual                acquisition conditions to be tested;            -   e23) processing of the reference image to create at                least a reference map at least partially representing                said discriminating information;            -   e24) comparison of the updated and reference maps so as                to determine a value for a first evaluation function,                said value for the first evaluation function being                dependent on the differences between said updated and                reference maps and corresponding to a decision as to                whether to continue or stop the search for virtual                acquisition conditions approximating said actual                acquisition conditions with greater precision than said                virtual acquisition conditions to be tested as                determined the last time step e21) was run;            -   e25) if said value for the first evaluation function                corresponds to a decision to continue said search,                modification of the virtual acquisition conditions to be                tested, then resumption from step e22);        -   e3) determination of a value for a second evaluation            function, said value for the second evaluation function            being dependent on the differences between the updated and            reference maps under the virtual acquisition conditions best            approximating said actual acquisition conditions and            resulting from the last running of step e2), said value for            the second evaluation function corresponding to a decision            to continue or stop the search for a reference model            approximating the positioning of the teeth at the time of            the acquisition of the updated image with greater precision            than said reference model to be tested that was used the            last time step e2) was run, and if said value for the second            evaluation function corresponds to a decision to continue            said search, modification of the reference model to be            tested by moving one or more tooth models, followed by            resumption from step e2);    -   the method comprises a step 9) in which the optimal switchover        moment, preferably the optimal scenario and/or the optimal        profile, are presented to a doctor, particularly an        orthodontist, and/or to the patient;    -   in step 1), a digital three-dimensional reference model is        defined for a gum from which said tooth models emerge, or “gum        model”, and, in step 4), said tooth models are moved and said        gum model is modified to deform the initial reference model;    -   in order to deform the initial reference model a deformation of        the gum model is calculated from said movements of said tooth        models;    -   Preferably, operations 4) and/or 5) and/or 6) and/or 7) and/or        8), preferably at least steps 4) and 5) and preferably 6), and        preferably 7), and preferably 8) are achieved with a computer;    -   preferably, an orthodontist commands the computer at step 2).

The invention also relates to a method of adapting an orthodonticaligner, in which method a method for determining an optimal switchovermoment according to the invention is implemented and then, according tothe result of said evaluation, an aligner suited to at least part of theorthodontic treatment of the teeth onwards from said optimal switchovermoment is manufactured.

The invention also relates to:

-   -   a computer program and, in particular, a specialist application        for a mobile telephone, comprising program code instructions for        executing one or more, preferably all, of operations 3) to 8)        when said program is run by a computer,    -   a computer medium on which such a program is recorded, for        example a memory or a CD-ROM; and    -   a computation tool, particularly a personal device, in        particular a mobile telephone or a tablet, on which such a        program is loaded.

For preference, the computation tool comprises a scenario simulator ableto create scenarios, to determine profiles of said scenarios, and toevaluate said scenarios with reference to an evaluation rule. Forpreference also, it comprises a “man-machine” interface and means fordetermining the evaluation rule from data input using said interface.

The invention also relates to a system comprising

-   -   a three-dimensional scanner capable of creating an initial        reference model, and    -   a computation tool, particularly a personal device, preferably a        mobile telephone, able to acquire an updated image and loaded        with a program according to the invention.

Definitions

“Remaining treatment” is understood to mean that part of the treatmentonwards from the current moment.

A “patient” is understood to mean any person for whom a method accordingto invention is implemented, whether this person is sick or not.

The “acquisition conditions” specify the position and the orientation inspace of an image acquisition apparatus relative to the patient's teeth(actual acquisition conditions) or to a three-dimensional model of teethof the patient (virtual acquisition conditions), and preferably thecalibration of this image acquisition apparatus. Acquisition conditionsare said to be “virtual”, or “simulated” when they correspond to asimulation in which the acquisition apparatus would be under saidacquisition conditions (virtual positioning and preferably virtualcalibration of the acquisition apparatus).

The “calibration” of an acquisition apparatus consists of the set ofvalues of the calibration parameters. A “calibration parameter” is aparameter intrinsic to the acquisition apparatus (unlike its positionand its orientation), the value of which influences the image acquired.Preferably, the calibration parameters are chosen from the group formedby the aperture, the exposure time, the focal length and thesensitivity.

A 3-D scanner is an apparatus that makes it possible to obtain athree-dimensional representation of an object.

What is meant by an “image” is a two-dimensional image such as aphotograph. An image is made up of pixels.

An updated image “corresponds to” a view of the updated reference modelwhen this view is substantially identical to said updated image.

The terms “comprise”, “include” or “have” should be interpreted broadlyand without limitation, unless specified otherwise.

BRIEF DESCRIPTION OF THE FIGURES

Additional features and advantages of the invention will become furtherapparent upon reading the following detailed description and fromstudying the attached drawing, in which:

FIG. 1 depicts various evolutions with respect to time for a positioningparameter relating to the positioning of a tooth, according to thenature of the remaining treatment considered;

FIG. 2 is a flow diagram illustrating the implementation of a predictionmethod according to the invention.

DETAILED DESCRIPTION

Operation 1) is preferably performed at the start of the treatment orbefore the start of the treatment and consists in creating a digitalthree-dimensional model of a dental arch bearing the teeth treated, or“initial reference model”.

The initial reference model is, for example, of the .stl or .Obj, .DXF3D, IGES, STEP, VDA, or scattergram type. Advantageously, such a model,referred to as a “3-D” model, may be viewed from any angle.

The initial reference model may be prepared from measurements taken fromthe teeth of the patient or from a physical model of his teeth, forexample a plaster cast.

The initial reference model is preferably created by means of aprofessional device, for example by means of a 3-D scanner, preferablyoperated by a healthcare professional, for example by an orthodontist,or an orthodontistry laboratory. In an orthodontist practice, thepatient or the physical model of his teeth may advantageously bearranged in a precise position and the professional device may beperfected. This results in a highly accurate initial reference model.The initial reference model preferably provides information regardingthe positioning of the teeth with an error of less than 5/10 mm,preferably less than 3/10 mm, preferably less than 1/10 mm.

In the initial reference model, a part which corresponds to a tooth, or“tooth model” is delimited by a gum edge which may be broken down intoan interior gum edge (on the side of the inside of the mouth in relationto the tooth), an exterior gum edge (facing toward the outside of themouth in relation to the tooth) and two lateral gum edges. The toothmodels may be defined as described, for example, in internationalapplication PCT/EP2015/074896.

For preference, the initial reference model also models the gumsurrounding the teeth. The part of the initial reference model thatrepresents the gum is referred to as the “gum model”.

Operation 2) comprises modifying the initial reference model, by movingthe tooth models, until a desired positioning of the teeth referred toas “target positioning” is obtained. The target positioning may be theone desired at the end of the treatment (“final set-up”) or at apredetermined intermediate stage in the treatment (“intermediateset-up”).

For preference, operation 2) also comprises a deforming of the gummodel. In one preferred embodiment, the deformation of the gum model is,at least in part, the result of a simulation obtained from the moving ofthe tooth models. Advantageously, the search for the updated referencemodel is thereby speeded up.

For preference, operation 2), subsequent to operation 1), is performedimmediately after operation 1).

Operations 3) and 4), subsequent to operation 2) have the objective ofupdating the initial reference model so that the tooth models are inpositionings identical to those of the actual teeth at the currentmoment.

In operation 3), an updated image of the part of the dental arch bearingthe teeth that are to be treated is taken, by means of an imageacquisition apparatus, under actual acquisition conditions.

The image acquisition apparatus is preferably a mobile telephone, a“connected” camera, a smartwatch, a tablet or a desktop or laptoppersonal computer, including an image acquisition system, such as awebcam or a camera.

The acquisition is preferably performed by the patient or someone closeto the patient, but may be performed by any other individual, notably adentist or an orthodontist, preferably without imposing a requirementfor the image acquisition apparatus to be positioned accurately withrespect to the teeth.

For preference, the updated image is a photograph or an extract from afilm. It is preferably in color, preferably true color.

For preference, in operation 3), the procedure is in accordance withstep b) described in PCT/EP2015/074896.

Operation 4), subsequent to operation 3), preferably consists in aniterative process in which, upon each iteration, one or more toothmodels are moved, then optimum conditions for observing the initialreference model thus modified (referred to as the “reference model to betested”) are determined, the optimum observation conditions beingdefined as the conditions allowing the reference model to be tested tobe observed in such a way that the view of said model is as close aspossible to the updated image.

For preference, on each iteration, the gum model is also deformed sothat the initial reference model modified by the movement of the toothmodels and the deformation of the gum model is as compatible as possiblewith the updated image.

In one embodiment, a first deformation of the gum model is calculatedaccording to the movement of the tooth models. The first deformation maybe sufficient. Otherwise, it is supplemented by a second deformation,preferably determined by means of a meta-heuristic, preferablyevolutionary, method, preferably by simulated annealing.

Steps c) to e) described in PCT/EP2015/074896 are preferablyimplemented:

-   -   c) analysis of the updated image and creation of an updated map        relating to discriminating information;    -   d) optionally, determination, for the updated image, of rough        virtual acquisition conditions approximating the actual        acquisition conditions of said updated image;    -   e) search, in the case of the updated image, for an updated        reference model corresponding to the positioning of the teeth at        the time of the acquisition of the updated image, the search        preferably being carried out by means of a meta-heuristic,        preferably evolutionary method, preferably by simulated        annealing.

All the features of steps c) to e) described in PCT/EP2015/074896 areapplicable.

According to step c), the updated image is analyzed so as to create anupdated map relating to at least one item of discriminating information.

“Discriminating information” is characteristic information that can beextracted from an image (“image feature”), conventionally through thecomputer processing of this image.

Discriminating information may exhibit a variable number of values. Forexample, outline information may be equal to 1 or 0 according to whetheror not a pixel belongs to an outline. Brightness information may adopt agreat many values. Image processing makes it possible to extract andquantify the discriminating information.

The updated map represents discriminating information in the frame ofreference of the updated image. The discriminating information ispreferably chosen from the group consisting of outline information,color information, density information, distance information, brightnessinformation, saturation information, information regarding reflectionsand combinations of this information.

In optional step d), the actual acquisition conditions for the updatedimage acquired in operation 3), namely the position and the orientationin space of the acquisition apparatus with respect to the teeth and thecalibration thereof are evaluated, roughly. Step d) advantageously makesit possible to limit the number of tests on virtual acquisitionconditions during step e) and therefore allows step e) to be speeded upconsiderably.

Use is preferably made of one or more heuristic rules. For example, forpreference, conditions that correspond to a position of the imageacquisition apparatus behind the teeth or at a distance greater than 1 maway from the teeth, are excluded from the virtual acquisitionconditions that can be tested for in step e). In a preferred embodiment,use is made of markers marked on the updated image in order to determinea substantially conical region of the space that delimits the virtualacquisition conditions that can be tested for in step e), or “testcone”.

The objective of step e) is to modify the initial reference model untilthere is obtained an updated reference model that corresponds to theupdated image, namely such that the tooth models can be observed asdepicted in the updated image. Ideally, the updated reference model istherefore a digital three-dimensional reference model from which theupdated image could have been taken had this model been real.

A succession of reference models “to be tested” is therefore tested, thechoice of a reference model to be tested being dependent preferably onthe level of correspondence between the previously tested referencemodels “to be tested” and the updated image. This choice is preferablymade by following a known optimization method, particularly chosen frommeta-heuristic optimization methods, preferably evolutionary methods,particularly from simulated annealing methods. The optimization methodsdescribed in PCT/EP2015/074896 can notably be used.

For preference, step e) comprises the following steps:

-   -   e1) definition of a reference model to be tested as being the        initial reference model, then    -   e2) following the subsequent steps, testing virtual acquisition        conditions with the reference model to be tested in order to        achieve a fine approximation of said actual acquisition        conditions;        -   e21) determining virtual acquisition conditions to be            tested;        -   e22) creation of a two-dimensional reference image of the            reference model to be tested under said virtual acquisition            conditions to be tested;        -   e23) processing of the reference image to create at least a            reference map at least partially representing said            discriminating information;        -   e24) comparison of the updated and reference maps so as to            determine a value for a first evaluation function, said            value for the first evaluation function being dependent on            the differences between said updated and reference maps and            corresponding to a decision as to whether to continue or            stop the search for virtual acquisition conditions            approximating said actual acquisition conditions with            greater precision than said virtual acquisition conditions            to be tested as determined the last time step e21) was run;        -   e25) if said value for the first evaluation function            corresponds to a decision to continue said search,            modification of the virtual acquisition conditions to be            tested, then resumption from step e22);    -   e3) determination of a value for a second evaluation function,        said value for the second evaluation function being dependent on        the differences between the updated and reference maps under the        virtual acquisition conditions best approximating said actual        acquisition conditions and resulting from the last running of        step e2), said value for the second evaluation function        corresponding to a decision to continue or stop the search for a        reference model approximating the positioning of the teeth at        the time of the acquisition of the updated image with greater        precision than said reference model to be tested that was used        the last time step e2) was run, and if said value for the second        evaluation function corresponds to a decision to continue said        search, modification of the reference model to be tested by        moving one or more tooth models, followed by resumption from        step e2).

Steps e1) to e3) are described in detail in PCT/EP2015/074896, orWO2016066651.

According to steps c) to e), the updated reference model is athree-dimensional model resulting from successive modifications to thevery precise initial reference model. Advantageously, it is thus itselfvery precise, even though it has been obtained from simple photographstaken without any special precautions.

These steps therefore make it possible, starting from one or more simpleimages of teeth, taken without precisely pre-positioning the imageacquisition apparatus with respect to the teeth, for example from aphotograph taken by the patient, to assess with precision the positionof the teeth at the current moment. This assessment may further be doneremotely, from simple photographs taken on a mobile telephone, withoutthe patient having to travel to the orthodontist's in person.

Operation 4) leads to an updated reference model representing the teethvery precisely, in the position they occupy at the current moment.

According to a first embodiment, the method continues with thesuccession of steps 5′) to 8′):

In step 5′), a set of remaining-treatment scenarios, namely scenariossuitable for achieving a tooth positioning site substantially identicalto that of the corresponding tooth models in the target reference modelis determined.

FIG. 1 depicts for example three evolutions with respect to time of thecoordinate x of a point on a tooth in space, as a function of theremaining treatment, namely of the treatment adopted onwards of thecurrent moment to. The target positioning of this point is achieved whenx is equal to x_(target).

Curve S₀ represents the evolution of x if the treatment continuesexclusively using an arch wire and brackets orthodontic appliance. Thisevolution is typical of this type of orthodontic appliance, with aneffectiveness progressively dropping off. The remaining treatment is thequickest, the target positioning being achieved at the moment t_(S0).However, the duration for which an arch wire and brackets orthodonticappliance is worn (t_(S0)−t₀) is the longest. Curve S₁ represents afirst scenario for a hybrid treatment. According to this scenario, thearch wire and brackets orthodontic appliance hitherto worn is replaced,at the current moment, by an aligner. The switchover moment t_(B1) istherefore equal to t₀. The remaining treatment then continuesexclusively using one or more aligners. The evolution of x isthenceforth substantially linear and illustrates the typicaleffectiveness of this type of orthodontic appliance.

The duration for which an arch wire and brackets orthodontic applianceis worn is advantageously zero. However, the remaining treatment is theslowest, the target positioning being achieved at the moment t_(S1).

Curve S₂ represents a second scenario for a hybrid treatment. In thisscenario, the arch wire and brackets orthodontic appliance is worn,during an arch-wire phase P_(A2), until a switchover moment 432, and isthen replaced with an aligner. The remaining treatment then continuesexclusively using one or more aligners (aligner phase P_(G2)).

The duration for which an arch wire and brackets orthodontic applianceis worn (t_(S2)−t_(B2)) and the duration of the remaining treatment aresomewhere between those of the previous two situations.

For preference, over 3, over 5, over 10, over 50 or over 100 hybridremaining-treatment scenarios are determined.

The remaining-treatment scenarios may be determined by an orthodontistand/or by means of simulation software capable of simulating the effectof various orthodontic appliances according to the updated positioningof the teeth and the target positioning, for example using the Insignia™software by the company Ormco™.

In step 6′), a profile is determined for each scenario determined instep 5′). A “profile” is made up of a set of values for evaluationparameters, namely ones which are relevant for evaluating a scenarioaccording to an evaluation rule.

The evaluation parameters may relate to the duration, to the cost, tothe pain and/or to the comfort and/or to the clinical severityassociated with each scenario.

Pain may be measured by means of a pain factor associated with thetreatment, for example evaluated from surveys taken from individuals whohave been treated in a similar way.

Comfort in particular may make reference to the esthetic impact of thetreatment. For example, the comfort factor may be the ratio between thetotal duration of the aligner phases and the total duration of thearch-wire phases for the remaining treatment.

The profile for scenario S₁ may for example be (duration of remainingtreatment= 3/10; comfort factor= 9/10; pain factor= 8/10; cost= 7/10).

The profile for scenario S₂ may for example be (duration of remainingtreatment= 7/10; comfort factor= 6/10; pain factor= 5/10; cost= 9/10).

In step 7′), the profiles are evaluated with reference to the evaluationrule. The evaluation rule is preferably established by the patient,according to the importance he attaches to the evaluation parameters. Itmay be established at any time before step 7′).

For preference, the acquisition apparatus asks questions of the patientand the answers to these questions allow it to define the evaluationrule.

The preferred profile, with reference to the evaluation rule, is said tobe “optimal”.

An evaluation rule may establish a condition. For example, an evaluationrule may dictate that the duration of the remaining treatment be under 6months or that the combined duration of the arch-wire phases of the fulltreatment must be under 2 months.

An evaluation rule may establish a conditional condition. For example,an evaluation rule may dictate that the duration of the remainingtreatment be longer than 6 months or that the combined duration of thearch-wire phases of the residual treatment must not exceed 2 months.

An evaluation rule may establish an optimization rule. For example, anevaluation rule may dictate a search for the shortest remainingtreatment, with the maximum duration of 1 month for treatment using anarch wire and brackets orthodontic appliance.

With this last example, scenario S₂ could prove optimal if the durationbetween t_(B2) and t₀ is 1 month.

Of course, an evaluation rule may be complex and establish, for example,that the combined duration of the arch-wire phases in the remainingtreatment be as short as possible, for a set total cost.

One evaluation rule could, in the example of FIG. 1, be to minimize thefunction F=k₁*Duration of remaining treatment+k₂*Comfort factor+k₃*Painfactor+k4*Cost, the weightings k_(i) preferably being determined by thepatient or by an algorithm, according to the patients' responses toquestions.

If k₁=1, k₂=2, k₃=1 and k₄=3, the function F for scenarios S₁ and S₂ isequal, respectively, to F(S₁)=50 and F(S₂)=51.

In step 8′), the evaluations of the profiles made in step 7′) arecompared so as to select a scenario considered to be optimal withreference to the evaluation rule. The switchover moment referred to as“optimal” t_(B)* associated with this optimal scenario may then beproposed, for example displayed on a screen.

In the example of FIG. 1, F(S₁) (=50) is less than F(S₂) (=51). Theprofile of S₂ is therefore optimal, S₂ is the optimal scenario, and theswitchover moment referred to as “optimal” t_(B)* is therefore t_(B2).

In a preferred embodiment, operations 5) to 7) are not performedsuccessively. Operations 5) to 8) are preferably performed in the formof steps 5″) to 8″).

More specifically, a first scenario is determined and its profileevaluated before a second scenario is determined. The second scenariomay thus advantageously be determined according to the evaluation of thefirst scenario.

For preference, the new remaining-treatment scenario is determined onthe basis of scenarios the profiles of which have been evaluatedbeforehand. For example, if the two scenarios evaluated beforehand showthat increasing the duration of the arch-wire phases impairs the scoreof the profiles with reference to the evaluation rule, for examplebecause this rule is highly influenced by a comfort factor, the newscenario will be looked for among the scenarios that offer a low totalduration for the arch-wire phases.

The search for an optimal scenario is thereby speeded up considerably.All known optimization methods can be used. The search for the optimalscenario preferably performed by means of a meta-heuristic, preferablyevolutionary, method, preferably by simulated annealing, preferably bymeans of a method described in PCT/EP2015/074896.

Steps 5″) to 8″) are particularly suitable when the creation ofscenarios and the evaluation of scenario profiles are automated in asimulator. For preference, such a simulator is programmed into acomputation tool, for example a computer or an acquisition apparatus,into which the evaluation rule has been programmed.

A scenario simulator may be created from statistical analyses ofhistorical data. In particular, a statistical analysis of historicaldata may be used to simulate the effect of a given orthodontic applianceon the positioning of the teeth, but also to define a profile, forexample a pain factor or comfort factor for the remaining treatmentaccording to the duration of the arch-wire phases or anoverall-treatment cost according to the durations of the arch-wire andaligner phases.

In one preferred embodiment, the method comprises a step 9) in which theoptimal scenario and/or the optimal profile, are presented to thepatient, preferably on a screen, preferably on the screen of his mobiletelephone. Of course, the method may lead to several optimal scenariosbeing determined. For preference, all the optimal scenarios and/oroptimal profiles are presented to the patient, preferably on theacquisition apparatus used in step 3).

If the patient is not satisfied, he may establish a new evaluation rule,for example by modifying the weightings k_(i), and resume the method atstep 5′) or 5″).

The optimal switchover moment for the optimal scenario adopted allowsthe remaining treatment to be adapted precisely to the needs of thepatient. In particular, it is possible to manufacture one or morealigners which could be used from this moment on.

As is now clearly apparent, the invention provides an effective way foroptimizing a hybrid orthodontic treatment according to an evaluationrule. Advantageously, this evaluation rule may take into considerationnumerous evaluation parameters, making it possible precisely to respondto the specific expectations of the patient. Finally, a method accordingto the invention may be programmed, particularly onto a mobiletelephone. At any moment, the patient may, remotely, perform evaluationsof various scenarios and decide accordingly when to switch over. Themethod may be implemented as many times as desired, for example morethan once, more than twice or more than five times per month.

The number of orthodontist appointments is also advantageously limited.

1. A method of adapting an orthodontic treatment of a patient,comprising the following steps: at a current moment, acquiring, with amobile phone, of at least one two-dimensional image of the teeth of thepatient, referred to as “updated image”, analysing of the updated image,and, from said analysis, creation, by a simulator programmed into acomputation tool, of remaining-treatment scenarios, each scenariocomprising, from a switchover moment onwards, at least one phase oftreatment using an orthodontic aligner; determining, by said simulator,of profiles of said scenarios, and evaluation, by said simulator, ofsaid profiles by means of at least an evaluation rule to determine anoptimal switchover moment to replace an orthodontic appliance worn bythe patient with an orthodontic aligner, and manufacturing theorthodontic aligner according to a result of said determination of theoptimal switchover moment, the orthodontic aligner being suited to atleast part of remaining-treatment of the teeth onwards from said optimalswitchover moment.
 2. The method according to claim 1, wherein a saidprofile for a said scenario comprises at least one value for anevaluation parameter selected from the group formed of: the duration ofthe remaining treatment of said scenario; the duration of the entiretreatment; a clinical-complexity factor; a pain factor for the remainingtreatment of said scenario, a pain factor for the entire treatment; theduration of the phase or phases of treatment using the orthodonticappliance during the remaining treatment; a comfort factor for theremaining treatment of said scenario, a comfort factor for the entiretreatment; a cost of the remaining treatment of said scenario, a cost ofthe entire treatment, a function of the preceding evaluation parameters.3. The method according to claim 1, wherein said remaining-treatmentscenarios are determined for moving said teeth from their positionrepresented in a three-dimensional updated reference model into theirposition represented in a three-dimensional target reference model. 4.The method as claimed in claim 3, the initial reference model or theupdated reference model being created by mean of a three-dimensionalscanner or by means of acquisition of two-dimensional images.
 5. Themethod according to claim 1, the determination of the optimal switchovermoment comprising the following operations: 1) at the start of thetreatment or before the start of the treatment, creating a digitalthree-dimensional model of at least part of a dental arch bearing saidteeth, or “initial reference model” and, for each of said teeth,defining a digital three-dimensional reference model of said tooth inthe initial reference model, or “tooth model”; 2) after operation 1),deforming the initial reference model, by moving the tooth models, untilsaid tooth models are in a target position, so as to obtain a “targetreference model”, 3) after operation 2), at said current moment in aphase of the treatment during which the patient wears an orthodonticappliance, acquiring said updated image, under actual acquisitionconditions; 4) deforming the initial reference model, by moving thetooth models, until said at least one updated image corresponds to aview of the initial reference model thus deformed, referred to as“updated reference model”; 5) determining, from said updated referencemodel and from said target reference model, a plurality ofremaining-treatment scenarios for moving said teeth from their positionrepresented in the updated reference model into their positionrepresented in the target reference model, each scenario comprising,from a switchover moment onwards, at least one phase of treatment usingan orthodontic aligner; 6) determining, for each scenario, a profilecomprising at least one value for an evaluation parameter selected fromthe group formed of: the duration of the remaining treatment of saidscenario; the duration of the entire treatment; a clinical-complexityfactor; a pain factor for the remaining treatment of said scenario, apain factor for the entire treatment; the duration of the phase orphases of treatment using the orthodontic appliance during the remainingtreatment; a comfort factor for the remaining treatment of saidscenario, a comfort factor for the entire treatment; a cost of theremaining treatment of said scenario, a cost of the entire treatment, afunction of the preceding evaluation parameters; 7) evaluating eachprofile by means of said at least one evaluation rule; and 8)determining, from the scenario the profile of which is optimal, or“optimal scenario”, said optimal switchover moment for replacing theorthodontic appliance with an orthodontic aligner.
 6. The method asclaimed in claim 5, comprising the following steps: 5″) determining,from said updated reference model and from said target reference model,a remaining-treatment scenario for moving said teeth from their positionrepresented in the updated reference model into their position in thetarget reference model, a remaining-treatment scenario comprising, froma switchover moment onwards, at least one phase of treatment using anorthodontic aligner; 6″) determining, for said scenario, a profilecomprising at least one value for an evaluation parameter selected fromthe group formed of: the duration of the remaining treatment of saidscenario the duration of the entire treatment; a clinical-complexityfactor; a pain factor for the remaining treatment of said scenario, apain factor for the entire treatment; the duration of the phase orphases of treatment using the orthodontic appliance during the remainingtreatment; a comfort factor for the remaining treatment of saidscenario, a comfort factor for the entire treatment; a cost of theremaining treatment of said scenario, a cost of the entire treatment, afunction of the preceding evaluation parameters; 7″) evaluating theprofile by means of at least one evaluation rule and, if the profile isnot optimal with reference to the evaluation rule, determining a newremaining-treatment scenario and resumption from step 6″); 8″)determining, from the scenario the profile of which is optimal, or“optimal scenario” of an optimal switchover moment for replacing theorthodontic appliance with an orthodontic aligner.
 7. The method asclaimed in claim 1, the orthodontic appliance being an arch wire andbrackets orthodontic appliance or an orthodontic aligner.
 8. Acomputation tool comprising a scenario simulator to create scenarios,the scenario simulator comprising program code instructions forexecuting the following steps: receiving at least one digitalthree-dimensional model of a patient called “reference model”,representing the configuration of the teeth of the patient before adental treatment or independently of any orthodontic treatment, for eachof said teeth, definition of a digital three-dimensional model of saidtooth in the reference model, called “tooth model”; deforming thereference model, by moving the tooth models, until said tooth models arein a target position, so as to obtain a target reference model,simulating from said reference model and from said target referencemodel, a plurality of scenarios for moving said teeth from theirposition represented in the reference model into their positionrepresented in the target reference model, each scenario comprising,from a switchover moment onwards, at least one phase of treatment usingan orthodontic aligner; determining of profiles of said scenarios, andevaluating of said profiles by means of at least an evaluation rule todetermine an optimal switchover moment to replace an orthodonticappliance worn by the patient with an orthodontic aligner.
 9. Thecomputation tool as claimed 8, wherein a profile comprises at least onevalue for an evaluation parameter selected from the group formed of: theduration of part or all treatment; a clinical-complexity factor; a painfactor for part or all treatment; the duration of the phase or phases oftreatment using an orthodontic appliance; a comfort factor for part orall treatment; a cost of part or all treatment, a function of thepreceding evaluation parameters.
 10. The computation tool as claimed inclaim 8, comprising a “man-machine” interface and means for determiningthe evaluation rule from data input using said interface.
 11. Thecomputation tool as claimed in claim 8, being an acquisition apparatus.12. The computation tool as claimed in claim 11, wherein saidacquisition apparatus is selected from the group consisting of a mobiletelephone, a connected camera, a smartwatch, a tablet and/or a desktopor laptop personal computer.
 13. The computation tool as claimed inclaim 11, the reference model being created from two-dimensional imagesacquired by said acquisition apparatus.
 14. The computation tool asclaimed in claim 8, comprising a three-dimensional scanner, thereference model being created with said a three-dimensional scanner. 15.The computation tool as claimed in claim 10, comprising a screen onwhich the optimal switchover moment and/or the related “optimal”scenario, and/or the related “optimal” profile are presented.